GEORGE TOWN: Getting a heterologous booster shot is safe and highly protective, says a virologist.

       The boosters would be crucial for the elderly and those with comorbidities and immunodeficiencies, said Universiti Sains Malaysia (USM) virologist Dr Kumitaa Theva Das.

       She cited a study in the United Kingdom where the antibody levels of those fully vaccinated and in their 60s began to wane as early as six weeks after the second shot.

       In some cases, she said, the efficacy rate fell more than 50% after 10 weeks.

       “Likewise, the antibody levels seem to be high among those aged 60 and above who got their booster shots in the United States, the UK and Israel.

       “This is apparent after six months of getting their booster jabs.

       “In other words, fully vaccinated people are like protected by a shield while those with booster doses will be protected by two shields,” she said.

       Booster doses began nationwide on Oct 13 for eligible individuals.

       Dr Kumitaa said studies in some countries had shown that the mix-and-match approach was not only safe but provided better protection.

       “In March this year, several countries carried out the heterologous method by giving out two different types of vaccines as first and second doses.

       “The results showed that such method is safe and highly protective.”

       Dr Kumitaa said the public could always sign up for the boosters first before consulting the doctors at the vaccine dispensing centres.

       “Tell them your concerns.

       “These doctors are always willing to explain and answer any question you may have and put you at ease in taking the booster shots,” she added.

       Dr Kumitaa said boosters most likely would not be needed if the healthcare system is still dealing with the original strain of the SARS-CoV-2 virus.

       She said the vaccines were developed to optimally work against that strain and was proven to be extremely effective.

       “But with Delta being the prevalent strain, together with new strains from neighbouring countries like Delta Plus, Lambda and Mu, they could reduce the immune protection,” she said.

       Dr Kumitaa said new Covid-19 variants are likely to emerge as long as there are unvaccinated people.

       “With new variants, this might push back how quickly a country is able to recover and when it can move to an endemic phase.

       “There is a higher probability for the virus to mutate in the body of unvaccinated people.

       “SARS-CoV-2 roughly mutates once in two weeks while for the Delta variant, it has shown that infection can last up to 18 days in the body of those unvaccinated people.

       “For those who have been vaccinated, even if they do get infected, the duration of infection tends to be shorter, roughly between five and seven days.

       “This reduces the possibility of new variants emerging with possible breakthrough infections,” she said.

       Penang Hospital infectious disease unit head Datuk Dr Chow Ting Soo said the Delta variant is the reason that booster jabs are needed as it is more transmissible and could reduce the vaccine and treatment efficacy.

       She said the efficacy of the Sinovac vaccine starts to wane after three months and six months for Pfizer or AstraZeneca.

       She also said that if the virus keeps mutating and changing, a regular vaccine jab might be needed in the future.

       “The virus is too new for all of us. Experts still don’t have an answer now on whether we need to be jabbed regularly,” she added.